1. Technical Field
The present invention relates to a semiconductor device and a method of manufacturing the semiconductor device and, more particularly, to a transistor having a cylinder type gate and a method of manufacturing the transistor.
2. Related Art
Thin film transistors (TFTs) are used as switching devices in flat panel display apparatuses such as liquid crystal display devices (LCDs) or organic light emitting display devices (OLEDs). Mobility or leakage current, by which the performance of the thin film transistors is evaluated, is greatly affected by the material and state of a channel layer through which charge carriers travel.
In commercially produced liquid crystal display devices, a channel layer of a thin film transistor comprises mainly amorphous silicon. When the channel layer of the thin film transistor comprises mainly amorphous silicon, charge mobility is about 0.5 cm2/Vs, which is very low, and thus it is difficult to increase the operating speed of such liquid crystal display devices.
Thus, a nano-wire transistor with a channel layer formed of a single-crystal semiconductor, and having a greater charge mobility than a channel layer formed of amorphous silicon, has been suggested.
In a nano-wire transistor, a gate electrode is formed on a substrate, and a gate insulating layer is formed on the substrate to cover the gate electrode. A plurality of channel layers, formed of a single crystal semiconductor on another substrate using a single crystal growth method and then cut, having a cylindrical shape are arranged on the gate insulating layer. A source electrode covering an end of the channel layers and a drain electrode covering another end of the channel layers are formed on the gate insulating layer.
As the channel layers of the nano-wire transistor are formed of a single crystal semiconductor, the charge mobility of the nano-wire transistor is excellent.
However, the channel layers are arranged in a multi-layer structure, and a gate electric field cannot be uniformly applied to the entire region of the channel layers. The portions of the channel layers near the gate electrode are more affected by the gate electric field than the portions of the channel layers far from the gate electrode. Thus not all of the channel layers can be uniformly turned on or turned off. Accordingly, it is difficult to realize a transistor having good switching characteristics.